There is widespread use of concave reflector structures that admit wave energy from distant objects and collect the energy for useful purposes. For the most part, these reflector structures have been used to receive solar heat waves and electromagnetic radio, radar, and television waves. Most, and probably very nearly all, of these reflectors have been built of relatively rigid materials such as metals. Usually the internal concave reflective surface of the structure is in the general form of a parabola which is constructed to focus reflected energy at or near a point on the central longitudinal axis of the parabola at a distance conveniently near the reflector structure. Often, the point of focus is in tne vicinity of the base of the parabola, where the base is termed to be the plane that perpendicularly intersects the axis and passes through the most "forward", front edge of the reflector structure.
Parabolic reflectors may be constructed in a wide range of sizes for use with various types of antenna feeds or energy collection systems including front mounted, cassegrain, or separately mounted focal point collectors or emitters. When used as an antenna, the reflector system may be designed to function in a wide variety of applications, such as: transmission and/or reception of all types of domestic or military radio, television, and microwave communication and control signals; stationary or mobile communication and control stations; and space erectible antenna systems. When used as a solar energy collector, the reflector system may be designed to focus the sun's rays on various types of heat exchangers or photovoltaic cells. Solar energy collectors may be designed in various sizes ranging from reflectors large enough to furnish heat and air-conditioning for homes and buildings to small pocket-size packages which may be inflated for heating food or water.
Prior art in the field of rhese reflector systems, includes the development and disclosure of inflatable reflector structures in which the concave reflector surface is constructed of a non-rigid flexible material, which is maintained in position and form by means other than the strength of the material itself.
The reflector surface may be maintained in shape, form, and position as part of an inflatable spherical balloon such as that shown in U.S. Pat. No. 2,814,038--Miller. In a similar manner, U.S. Pat. No. 3,548,706--Cover Jr. et al. discloses an electrostatic means for maintaining the flexible reflector surface in position and form.
U.S. Pat. No. 3,125,758--Koehler, reveals an inflated antenna structure of a selected special shape in which the pattern of the material, i.e. the shape of the balloon surface, is constructed to bring the surface of the balloon parallel to the longitudinal axis of the reflector at the peripheral edge. This is said to overcome problems of forming the inflated shape at or near the peripheral edge eliminating the need for a rim.
U.S. Pat. No. 3,056,131--McCreary, shows an inflatable antenna having an fixed external rim and an externally supported energy collector. U.S. Pat. No. 3,413,645--Koehler, discloses an inflatable antenna of a still different elongated shape and form.
U.S. Pat. No. 2,977,596 reveals still another inflatable antenna having internal ribs or webs to maintain the reflector in proper form.
Reflector structures of the concave parabolic configuration have in recent years become known under the term "dish", and have been used to receive electromagnetic energy waves as concentrating antennas in many situations. Such structures have also been used as solar reflectors which receive and concentrate energy waves from the sun as a source of heat. However, the primary interest in inflatable reflectors has been for use as an antenna, probably because there has been more a rapidly developed interest in electromagnetic wave energy, since this is more readily concentrated in usable form than solar energy.
Most recently, reflecting satellites have been placed in orbit for the purpose of being a source of either radio or television signals. These satellites receive signals from transmitting stations on earth and reflect them back as a second source for receiving dish antennas on the earth. In recent years there has been a growing interest in individual use i.e. family or small group reception of these signals for immediate viewing on television and radio receivers. Various forms of dish antenna are being marketed for this purpose. It is perceived that there is a need for an inflatable antenna which overcomes the problems presented by previous inflatable reflector structures, and meets the objects of providing an antenna that is lighter in weight, more portable, more convenient to use, and less expensive to manufacture and sell, without the loss of structural integrity and performance that is usually associated with more flexible inflated structures.
It is a purpose of this invention to meet these objectives in the construction of a novel inflatable reflector structure, a supporting structure for an inflatable reflector system, and a method of constructing concave parabolic reflector membranes for use in a inflatable reflective structure.
Major advantages of the inflatable reflector and mount system as compared with rigid reflector structures are: greatly reduced weight and cost; perfectly formed reflector surfaces; capability for folding, storing, and shipping in a small package; capability for mounting on a variety of bases or platforms, such as rooftops; and capability for rapid remotely controlled stowing in an unobtrusive or sheltered position when not in use or in adverse weather.
More specifically it is an important object to provide an inflatable, portable, inexpensive, relatively rigid dish antenna for individualized use in receiving signals from satellites stationed above the earth.